1. Technical Field
The present invention relates to improve an electrophoretic display device.
2. Related Art
An electrophoretic display device has an element substrate on which a plurality of pixel electrodes are formed, an opposing substrate that is provided so as to oppose the element substrate, and an electrophoretic layer placed between these substrates. A common electrode is formed on a face of the opposing substrate opposing to the element substrate. The electrophoretic layer is made of a dispersion medium and more than one kind of charged electrophoretic particles dispersed in the dispersion medium.
JP-A-2004-94168 and JP-A-2004-157450 are examples of related art. As described in the examples, when an electric potential difference is given between the common electrode and the pixel electrode, the charged electrophoretic particle is drawn to either one of the electrodes depending on the direction of the electric field. When the electrophoretic particle is colored and the electrode is made of a transparent material, the color of the electrophoretic particle drawn to either the common electrode or the pixel electrode can be observed. Thereby, an image can be displayed by controlling the voltage applied to each pixel electrode.
When the image displayed by the electrophoretic display device is reset and a new image is formed, the reset is sometimes carried out insufficiently depending on the state of the displayed image before the reset, producing an afterimage which is persistence of a part of the image previously displayed. Furthermore, the contrast tends to be deteriorated when an image is retained by making the potential difference of 0 [V] between the common electrode and the pixel electrode after resetting the previous image with, for example, negatively charged white particles. This happens because the white particles start to diffuse when the image is retained and a white level turns to gray.